I'm pretty sure they fight like infantry. Though i'm not certain if they truly fight at double strength like they are supposed to or not. I feel like it may be broken but since they don't give us the battle formulas i can't be certain if they are working as they are supposed to or if they are simply fighting at normal strength. They also aren't clear on that ability. Does outnumbered mean they have more berserker than you, they have more provisions than you or does it mean the total number of units is greater? I just know they are so expensive that it takes so long to get a significant number of them that i hardly ever use them.